| Glenoid fossa | |
|---|---|
 Costal surface of left scapula. Glenoid cavity shown in red. | |
 | |
| Details | |
| Identifiers | |
| Latin | cavitas glenoidalis, fossa glenoidalis |
| MeSH | D061165 |
| TA98 | A02.4.01.019 |
| TA2 | 1162 |
| FMA | 23275 |
| Anatomical terms of bone | |
Theglenoid fossa of the scapula or theglenoid cavity is a bone part of theshoulder. The wordglenoid is pronounced/ˈɡliːnɔɪd/ or/ˈɡlɛnɔɪd/ (both are common) and is fromGreek:gléne, "socket", reflecting the shoulder joint'sball-and-socket form.[1] It is a shallow,pyriformarticular surface, which is located on thelateral angle of thescapula. It is directed laterally and forward and articulates with thehead of thehumerus; it is broader below than above and its vertical diameter is the longest.
This cavity forms theglenohumeral joint along with thehumerus. This type of joint is classified as asynovial,ball and socket joint. The humerus is held in place within the glenoid cavity by means of the long head of thebiceps tendon. This tendon originates on the superior margin of the glenoid cavity and loops over the shoulder, bracing humerus against the cavity. Therotator cuff also reinforces this joint more specifically with thesupraspinatus tendon to hold the head of the humerus in the glenoid cavity.
The cavity surface is covered withcartilage in the fresh state, and its margins, slightly raised, give attachment to afibrocartilaginous structure, theglenoid labrum, which deepens the cavity. This cartilage is very susceptible to tearing. When torn, it is most commonly known as aSLAP lesion which is generally caused by repetitive shoulder movements.
Compared to theacetabulum (at the hip-joint) the glenoid cavity is relatively shallow. This makes theshoulder joint prone todislocation (luxation). Strongglenohumeral ligaments andmuscles prevents dislocation in most cases.
By being so shallow the glenoid cavity allows the shoulder joint to have the greatest mobility of all joints in the body, allowing 120 degrees of unassistedflexion. Additional range of motion in shoulder flexion (typically up to 180 degrees in humans) is also accomplished by the great mobility of thescapula (shoulder blade) through a process known as scapulohumeral rhythm.[2]
Interpretations of the fossil remains ofAustralopithecus africanus (STS 7) andA. afarensis (AL 288-1; a.k.a.Lucy) suggest that the glenoid fossa was oriented more cranially in these species than in modern humans. This reflects the importance of overhead limb postures and suggests a retention ofarboreal adaptations in thesehominoid primates, whereas the lateral orientation of the glenoid in modern humans reflects the typical lowered position of the arm.[3]
Indinosaurs the main bones of thepectoral girdle were thescapula (shoulder blade) and thecoracoid, both of which directly articulated with theclavicle. The place on the scapula where it articulated with thehumerus (upper bone of the forelimb) is called the glenoid. The glenoid is important because it defines the range of motion of the humerus.[4]
.gif)
This article incorporates text in thepublic domain frompage 207 of the 20th edition ofGray's Anatomy(1918)
